The invention herein described was made in the course of or under a contract or subcontract thereunder, with the United States Department of the Air Force.
1. Field of the Invention
The present invention is related to the field of adhesives or interlayers for safety laminates used as windows and windshields in vehicular, aircraft, armor, architectual and related applications. More particularly, it is related to adhesives for laminates of glass and/or plastic made from a cross-linked terpolymer of ethylene/vinyl acetate/vinyl alcohol.
2. Description of the Prior Art
Previously ethylene/vinyl acetate/vinyl alcohol terpolymer adhesives useful with glass, polycarbonate and other transparent plastics, were shown to be useful as an aircraft glazing interlayer from -65.degree. F. to 165.degree. F. The new transparent adhesive films of this invention have a greatly extended temperature utility range as an aircraft glazing interlayer of -65.degree. F. to at least 350.degree. F. The improved mechanical performance to 350.degree. F. introduced no changes in the basic (550.degree. F.) thermal stability or transparency of the ethylene terpolymer. A closely related prior art patent is U.S. Pat. No. 3,923,757 which provides transparent peroxide cross-linked ethylene/vinyl acetate/vinyl alcohol adhesive interlayers for making glass and polycarbonate laminates useful from -65.degree. F. to 165.degree. F., but not useful at temperatures appreciably above 165.degree. F.
There is much prior art in the general area ethylene/vinyl acetate/vinyl alcohol terpolymers including crosslinking of such polymers, e.g. U.S. Pat. No. 2,399,653 teaches partially hydrolyzed ethylene/vinyl acetate copolymers and they can be used as safety glass interlayers. This patent also teaches that they may be insolubilized or cured by means of crosslinking agents.
U.S. Pat. No. 2,448,946 teaches partially hydrolyzed ethylene/vinyl acetate copolymers and the crosslinking of these polymers with peroxides. These compositions are stated to be useful for a number of purposes including safety glass interlayers.
U.S. Pat. No. 3,378,515 teaches partially hydrolyzed copolymers of ethylene and vinyl acetate crosslinked with aromatic diisocyanates. These resins are stated to be particularly useful as ring seals in hydraulic systems because of solvent resistance and it is also stated that they can be used as adhesives for glass of cellulosic laminates.
U.S. Pat. No. 3,382,215 teaches a broad range of what are stated to be virgin olefin polymers modified with organic polyisocyanates. Among the examples are partially and completely hydrolyzed ethylene/vinyl acetate copolymers crosslinked with isocyanates. Among the uses for these polymers is as laminate interlayers for a wide variety of materials including polymeric, cellulosic and glass surfaces.
U.S. Pat. No. 3,622,440 teaches laminates especially useful for automobile windows and windshields prepared from glass and polycarbonate resin sheets using ethylene/vinyl acetate copolymer interlayers. A third comonomer can be included and among the many other third comonomers mentioned is vinyl alcohol. An organosilicon compound is specified as an adhesion promoting agent and a source of free-radials for crosslinking. The organosilicon compound can be a silyl peroxide in which case both the silicon and source of free-radicals is provided by the silicon compound. Crosslinking can also be provided by irradiation.
U.S. Pat. No. 3,631,161 teaches crosslinking ethylene-containing polymers with a silyl peroxide and among the many ethylene-containing polymers named is partially hydrolyzed ethylene/vinyl acetate copolymer.
U.S. Pat. No. 3,666,614 teachings are much the same as U.S. Pat. No. 3,622,440 which was filed the same day with the same inventors.